Esters thereof



' nitcd Statics Patent i .fffifalifi is preferred. The reaction may beefiected by simply 2,948,743 admixing the reactants in the solvent atroom tempera- POLYENE DICARBOXYLIC ACIDS D ture or at a slightlyelevated temperature. ilt is advan- ESTERS THEREOF tageous to displacethe air over the reaction mixture with 5 an inert gas such as nitrogen.Waldemar Gllexa Boflmmgena 151, Base], Rudolf The adduct which resultsfrom the reaction of the Riiegg, Bottmingen, and Gottlieb Ryser, Basel,Switdialdeh I yde and the phosphorane gradually decomposes zerland,assignors to Holfmann-La Roche Inc., Nutley, at me te perature into thedesired polyene dicam a corporation of New'Jel-Sey boxylic acid dialkylester and the corresponding triaryl- No Drawing. Filed Nov. 24, 1958,Ser. No. 775,695 phosphine oxide. Heating accelerates the decompositionof the adduct. It is preferable to elfect the de- Clalms pnontyapphcatmn Swltzefland 1957 composition of the adduct by gently boilingunder re- 13 Claims. (C. 260485) flux a methylene dhloride solutionthereof for several hours.

This invention relates to polyene dicarboxylic acids 15 When a dialkylester containing a central triple bond and esters thereof. Moreparticularly, the invention reis obtained, the triple bond may bepartially hydrogenated lates to polyene dicarboxylic acids containing30, 34 or to a double bond through the use of a selective hydrogen- 40carbon atoms and dialkyl esters of sudh acids. These ation catalyst suchas a lead-palladium catalyst in the esters and acids may be representedby the following presence of quinoline [Helv.Chim. Acta 35, 446 (1952)].two structural formulae: The hydrogenation may be carried out in aninert orwherein R, beginning with methyl, represents alternately ganicsolvent such as ethyl acetate, toluene, petroleum methyl or hydrogen, Rrepresents hydrogen or alkyl, and ether, etc. The resulting compoundhaving the cis conn represents an integer from 1 to 3, in each of thefiguration about the carbon atoms formerly joined by .above formulae. 35the triple bond, usually obtained from the hydrogenation,

The compounds of this invention are produced by may be isomerized to theall-trans compound, for excondensing 2,6,11,15 tetramethyl2,4,6,l0,12,14 hexaample, by heating. decahexaen 8 yn 1,16 dial or2,6,11,15 tetramethyl- The polyene dicarboxylic acid ester may besaponi- 2,4,6,8,1(),12,14 hexadecaheptaen 1,16 dial with a fied to thecorresponding dicarboxylic acid by reacting triaryl-phosphorane of thegroup 3-carbalkoxy-2-buten-4 with a base, e.g. an alkali metal hydroxidesuch as so- 1 yl triaryl phosphorane, 5 carbalkoxy 3 methyldiumhydroxide. Preferably this is effected by dissolv- 2,4 pentadien l yltriaryl phosphorane and 7- ing the ester in an inert organic solvent,ether for excarbalkoxy 3 methyl 2,4,6 octatrien 1 ylample, and treatingit with an alcoholic solution of triaryl-phosphorane and decomposing theadduct formed alkali metal hydroxide, methanolic sodium hydroxide soas aproduct of the condensation. The product of this lution, for example, atroom temperature in an inert reaction is a diester. The ester thusproduced may be atmosphere, e.g. under nitrogen. I converted to thecorresponding polyene dicarboxylic acid The phosphoranes referred toabove are derived from by saponification. the correspondingtriaryl-phosphoni'um halides by split- When the dialdehyde containing acentral triple bond is ting out hydrogen halide. .Thus3-carbalkoxy-2-buten-1- used in the condensation with thetriaryl-phosphorane, yl triaryl-phosphorane is obtained fromB-carbalkoxythe resulting diester similarly contains a central triple 2buten 1 yl triaryl phosphonium halide, 5-

bond. This ester may, if desired, be converted to the carbalkoxy 3methyl 2,4 pentadien 1 yl tricorresponding polyene diester having onlydouble bonds aryl-phosphorane is derived from 5-carbalkoxy-3-methylin aconjugated system by selectively hydrogenating the2,4-pentadieu-1-yl-triaryl-phosphonium halide and 7-car-- central triplebond to a double bond. The diester rebalkoxy 3 methyl 2,4,6 octatrien 1yl triarylsulting from the selective hydrogenation in general hasphosphorane is obtained from 7-carbalkoxy-3=methyl-2,- the cisconfiguration about the carbon atoms formerly4,6-octatrien-1-yltriaryl-phosphonium halide. The trilinked by thetriple bond. This compound may be aryl-phosphonium lhalides may beproduced by condensconverted to one having the all-trans configurationby ing the appropriate halogenated ester, e.g. 'y-halotiglicisomerization. The diester obtained via the dialdehyde acid alkyl ester,with a triaryl-phosphine; e.g. triphenylcontaining the triple bond andthe hydrogenation reacphosphine, in an inert solvent such as benzene.tion may similarly be converted to the'diacid by saponi- The conversionof the triaryl-phosphonium halide to fication of'the ester groups. thetriaryl-phosphorane by splitting out hydrogen halide The condensation of2,6,1l,15-tetramethyl-2,4,6,l0,- may be effected by treating the formerwith a metallo 12,14 hexadecahexaen 8 yn 1,16 dial or 2,6,11,15- organiccompound, for example, phenyl lithium or butyl tetramethyl2,4,6,8,l0,12,14 hexadecaheptaen 1,16- lithium, or with an alkali metalalcoholate, for example, dial with the phosphoranes named above may beeffected sodium methyla-te. Preferably the dehydrohalogenation by addingone molar proportion of the dialdehyde to at is carried out in an inertorganicsolvent such as ether,; least two molar proportions of thephosphorane, preferalcohol or especially methylene chloride with theexclu-.

ably an excess of the latter, in an inert organic solvent, sion ofoxygen.

such as ether, petroleum ether, benzene, methylene chlo Thetriaryl-phosphorane may be advantageously formed,

ride, dioxan, tetrahydrofuran, etc. Methylene chloride in situ and tothe reaction mixture may be added the wherein m represents an integerfrom 1 to 3 and R beginning with methyl, represents alternately methyland hydrogen, into the corresponding triaryl-phosphorane and adding tothe reaction mixture in which the phosphorane has been produced,2,6,11,15-tetramethyl-2,4,6,10,12,14- hexadecahexaen-8-yn-1,16-dial or2,6,11,15-tetramethyl- 2,468,10,12,14-hexadecaheptaen-1,16-dial anddecomposing the adduct formed as a product of the condensation. Thediester thus derived may be converted to the corresponding dicarboxylicacid by saponification as described above.

As a result of the reactions discussed, there may be obtained2,6,10,15,19,23hexamethyl-2,4,6,8,10,12,14,16,18,20,22-tetracosaundecaen-1,24-dioic acid, 2,6,10,15,19, 23 hexamethyl2,4,6,8,10,14,16,18,20,22 tetracosadecaen 12 yn 1,24-dioic acid,3,7,11,16,20,24-hexamethyl 1,3,5,7,9,11,15,17,19,21,23,25hexacosadodecaen-13-yn- 1,26-dioic acid,3,7,11,16,20,24-hexamethyl-1,3,5,7,9,11, 13,15,17,19,21,23,25hexacosatridecaen-1,26-dioic acid, 2,6,10,14,19,23,27octamethyl-2,4,6,8,10,12,14,18,20,22, 24,26,28,30 dotriacontatetradecaenl6-yn-1,32-dioic acid and2,6,10,14,19,23,27,31-octamethy1-2,4,6,8,10,12,14,16,18,20,22,24,26,28,30 dotriacontapentadecaen 1, 32-dioic acid, anddialkyl esters thereof.

In the discussion above, the term alkyl refers to straight chain andbranched chain aliphatic hydrocarbon groups such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cetyl, lauryl,octadecyl and the like, preferably up to about 18 carbon atoms. Loweralkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,amyl, etc., are most preferred. The aryl groups in thetriaryl-phosphoranes discussed above include such monocyclic arylradicals as phenyl, lower alkyl phenyl, wherein the lower alkyl groupis, for example, methyl, ethyl, propyl, isopropyl, and the like, andlower alkoxyphenyl, wherein the lower alkoxy group is, for example,methoxy, ethoxy, propoxy, isopropoxy, and the like. Phenyl is thepreferred aryl group. The term carbalkoxy as used above refers to thealkoxy radical ii3 Ra wherein R represents the alkyl groups definedabove. The halogen atom in the triaryl-phosphonium halide may be any ofthe halogenschlorine, bromine, iodine, and fluorine.

The diester and diacids obtained according to this invention arecrystalline red-to-violet colored compounds and are useful as coloringagents, e.g. for foodstuffs. They are also useful as additives foranimal feeds such as poultry feeds, e.g. for heightening the color ofegg yolk, skin, shank, meat and fatty tissue. The compounds having notriple bond also have vitamin A activity.

The following examples are illustrative of the invention. Alltemperatures are in degrees centigrade.

Example 1 20 parts by weight of 2,6,1l,15-tetramethyl-2,4,6,10,12,14-hexadecahexaen-8-yn-1,16-dial were suspended in 400 parts by volumeof synthetic toluene and shaken in the presence of 2 parts by volume ofquinoline and 4 parts by weight of palladium-lead catalyst in a hydrogenatmosphere until the absorption of hydrogen ceased. The mixture wasfiltered and the filter cake was extracted several times with chloroformwhile boiling. The chloroform solution was concentrated to a smallvolume and, upon treatment with ethyl acetate, 2,6,11,15-tetramethyl-2,4,6,8,10,12,14-hexadecaheptaen-1,16-dial crystallized in the form ofviolet flakes, M.P. 190191.

7.5 g. of lithium were dissolved in 1000 ml. of liquid ammonia andacetylene was bubbled through the solution. Within 30 minutes a solutionof g. of B-acetylacrylic acid methyl ester in 500 ml. of absolutediethyl ether was added dropwise. One half of the ammonia was allowed toevaporate and 70 g. of ammonium chloride were added. Then, the solutionwas diluted with 250 ml. of absolute ether and hydrolysed with 400 ml.of a saturated ammonium chloride solution. The ether layer was driedwith sodium sulfate and the solvent was driven off. The sirupy residuewas dissolved in 300 ml. of ethyl acetate and hydrogenated in thepresence of 2 g. of Lindlar catalyst. There was obtainedl-carbomethoxy-B-methyl- 3-hydroxy-1,4-pentadiene of B.P. 70-75 0.03mm., n =1.4672. This compound was dissolved in absolute ethanol andtreated with phosphorus tribromide to form 1 carbomethoxy 3 methyl5-bromo-1,3-pentadiene; n =l.5385.

19.5 g. 1-carbomethoxy-3-methyl-5-bromo-1,3-pentadiene were added to asolution of 24 g. of triphenyl-phosphine in 120 ml. of ethyl acetate andthe mixture was permitted to stand at room temperature for 24 hours. 1-carbomethoxy 3 methyl-1,3-pentadien-1-yl-triphenylphosphonium bromideprecipitated in the form of a crystalline cake which Was used directlyin the next step after decanting off the supernatant liquid. Thephosphonium bromide was dissolved in ml. of methylene chloride andtreated with 31 ml. of a 2 N solution of sodium methylate in methanolunder a current of nitrogen. The mixture was stirred for one hour atroom temperature and then a solution of 6 g. of2,6,11,15-tetramethyl-2,4,6, 8,10,12,14 hexadecaheptaen 1,16-dial in 100ml. of methylene chloride was quickly added. The mixture was stirred forone hour at room temperature and then re fluxed for five hours.

After cooling, the deep red reaction solution was washed with 200 ml. ofwater, dried and filtered through neutral aluminum oxide (activity stage5). The adsorbent was washed with methylene chloride solution and theclear filtrate was treated with 150 ml. of ethanol. The methylenechloride was then distilled off until crysta1- lization began. Themixture was permitted to stand for two hours in an ice bath and thecrystalline slurry which formed was then filtered oif under suction. Itwas washed with alcohol, with low boiling petroleum ether and dried invacuo at 3040. The 1,26-dicarbomethoxy-3,7,11, 16,20,24 hexamethyll,3,5,7,9,1l,l3,l5,17,19,2l,23,25- hexacosatridecaene melted at 199; UV.absorption maxima at 450, 478 and 513 mg E{=2425, 3675 and 3380 Byconcentrating the mother liquor and chromatographing the residue onneutral, weakly active aluminum oxide in benzene-methylene chloride, anadditional quantity of the product having the melting point l85l90 wasobtained.

Example 2 By the procedure described in Example 1, 19.5 g. of 1carbomethoxy 3-methyl-5-bromo-1,3-pentadiene and 24 g. oftriphenyl-phosphine were converted to l-carbomethoxy 3methyl-1,3-pentadien-l-yl-triphenyl-phos phonium bromide and similarlyconverted to the corresponding phosphorane by means of sodium methylatesolution. The phosphorane was treated with 6 g. of 2,6,11, 15tetramethyl 2,4,6,10,12,14-hexadecahexaen-8-yn- 1,16-dial. The reactionmixture was worked up in the same manner as in Example 1.1,26-dicarbomethoxy-3, 7,11,16,20,24 hexamethyl1,3,5,7,9,l1,15,17,19,2l,23, 25-hexacosadodecaen-13-yne was obtained inthe form of fine, red-brown crystals, M.P. 178-180; U.V. maxima at 457and 484 m E=2740 and 2460 5.5 g. of 1,26dicarbometh0xy-3,7,11,16,20,24-hexamethyl 1,3,5,7,9,11,15,l9,2l,23,25hexacosadodecaen- 340 m 1 574 (sis-peak); 518 m eipal maximum) 1 2610(prin- Upon boiling for several hours in petroleum ether under nitrogen,the cis-peak disappeared and after crystallization frommethanol-methylene chloride, the 1,26-dicarbomethoxy 3,7,11,16,20,24hexamethyl 1,3,5,7, 9,11,13,15,l7,19,21,23,25 hexacosatridecaeneobtained was identical withthe product of Example 1.

Example 3 7.5 g. of lithium were dissolved in 1000 ml. liquid ammoniaand acetylene was bubbled through the solution. Within 30 minutes asolution of 140 g. of fi-acetylacrylic acid ethyl ester in 500 ml.absolute diethyl ether was added dropwise. One half of the ammonia wasallowed to evaporate and 70 g. of ammonium chloride were added. Then thesolution was diluted with 250 ml. of absolute diethyl ether andhydrolysed with 400 ml. of a saturated ammonium chloride solution. Theaqueous layer was extracted with diethyl ether, the ether extractscollected, washed with saturated ammonium chloride solution, dried withsodium sulfate, filtered and then concentrated to dryness. There wereobtained 135 g. of 1 carbethoxy 3 methyl l pentaen 4 yn- 3 olof 15: :14710. 168 g. of the acetylenic carbinol were mixed with 168 ml. ofdihydropyrane. 2 ml. of 84% phosphoric acid were added while stirring.The temperature of the solution was kept between 20 and 30 and storedovernight at room temperature. The mixture was extracted with 300 ml. ofdiethyl ether and the extract washed to netural reaction with a mixtureof sodium chloride and sodium bicarbonate solution, then dried withsodium sulfate, filtered, concentrated and distilled in aVigreux-column. There were obtained 200 g. of fl tetrahydropyranyl etherof BF. 8590/0.05 mm. 252 g. of this product were hydrogenated in 500 ml.of petroleum ether (boiling range 40-60) in the pressure of 3 g.ofLindlarcatalyst. There were obtained 250 g.of.1-carbethoxy-3methyl-3-tetrahydropyranyloxy 1,4 pentadiene; n9=1.4700. This product was poured into 2000 ml. of dry diethyl ether anda solution of 38 g. of lithium aluminum hydride in 500 ml. of diethylether was dropwise added at a temperature of 20 to 10. 500-ml. of waterwere added and the mixture dissolved in 1000 ml. of 18% aqueous aceticacid. The aqueous layer was extracted with 250 ml. of ether, the etherextract washed netural with sodium dicarbonate solution, dried withsodium sulfate and the solvent evaporated. There were obtained 210 g. of4-methyl-4-tetrahydropyranyloxy 2,5 hexadiene-l-ol; n 1.4820; B.P.85-790. 7 1000 g. of manganese dioxide were suspended in 4000 ml. of lowboiling petroleum ether, 212 g. of the hexadienol were added .and themixture was allowed to react at room temperature for 4 hours. Afterfiltration, drying with sodium sulfate and evaporating off the solventthere were obtained 180 g. of4-methyl-4-tetrahydropyrany-loxy-2,5-hexadien-l-al; n =1.-482O;absorption maximum at 220 m =670 (in ethanol) 100 g. of the hexadienal,500 ml. of absolute benzene and 170 g. of(u-carbethoxy-ethylidene)-triphenyl-phos- O CH: CH3

I alkyl phoranewereheated for 5 hours under reflux. The solvent waseliminated in vacuo and the residue dissolved in 500 ml. of methanol.Then, there were added 125 ml. of water and 1000 ml. of petroleum ether(boiling range 40-50), and the 'mixture was agitated. Theaqueous-methanolic layer was separated, the ether layer was washedconsecutively with methanol and with water, dried with sodium sulfateand the petroleum ether evapo rated. The product was a yellowish oil (n=1.5170), which was stirredin 430 ml. of ethanol. The temperature waskept under 5 and 250 ml. of 62% hydrobromic acid were added. Afterstirring for two hours at 0-5, the mixture was poured into 1000 ml. ofice 0 water. The product was extracted with 500 ml. petroleum ether, theextract washed with water to neutral reaction, dried with calciumchloride and the solvent evaporated in vacuo at 20-25. The productobtained g.) was 3-methyl-7-carbethoxy-2,4,6 octatrien 1 yl bromide; n=1.5430; absorption maximum at 300 mp;

=950 (in petroleum ether) This product was dissolved in 600 ml. ofbenzene. 120 g. of triphenyl phosphine were added and the mixture wasagitated until dissolution was complete. On storing overnight theproduct crystallized. The crystals were collected by filtration undersuction, washed with benzene and then with petroleum ether (boilingrange 40- 50). After drying in vacuo at 50 there were obtained 138 g. of7-carbethoxy-3-methyl-2,4,6-octatrien-1-yl-triphenyl-phophonium bromide.

10 g. of7-carbethoxy-3-methyl-2,4,6,-octatrien-1-yl-t.riphenyl-phosphoniurnbromide in 100 ml. of dry methylene chloride were reacted with 9 ml. ofa 2 N solution of sodium methylate in methanol according to theprocedure in Example 1 and then treated with 3 g. of 2,6, 11,15tetramethyl 2,4,6,8,l0,12,14-hexadecaheptaen-1, 16-dial in 50 ml. ofmethylene chloride and the reaction product was worked up as describedin Example 1. 2,6, 10,14,19,23,27,31 octamethyl 2,4,6,8,10,12,14,16,18,

20,22,24,26,28,30 dotriacontapentadecaen 1,32 dioic 1 acid diethyl esterwas obtained in the form of violet crystals, MLP. 229-230; U.V.absorption maxima at;

498, 527 and 565 mu,

i=2465, 3235 and 2600 200 mg. of the ester obtained above wassaponifiedbystirring'in 140 ml. of ether and 40 ml. of a 10% meth-.anolic potassium hydroxide solution for 24 hours at 30 in a nitrogenatmosphere. The mixture was diluted with 300 ml. of water. The potassiumsalt was obtained as a suspension in the aqueous layer. The latter waswashed with ether, acified with 40 ml. 3 N sulfuric acid and extraotedthree times with methylene chloride. The collected methylene chlorideextracts were washed with water to netural reaction, dried with sodiumsulfate, filtered and the solvent driven ofi in vacuo. There wasobtained mg. of 2,6,10,14,19,23,27,3l octamethyl-2,4,6,8,10,12,14,16,18,20,22,24,26,28,30 dotriacontapentadecaen-1,32-dioicacid; M.P. 230; U.V. maxima at 497, 524 and 561 mu.

we claim:

1. A process which comprises condensing 2,6,11,15- tetramethyl2,4,6,10,12,14 hexadecahexaen 8-yn-l,l6- dial with a member of the groupconsisting of 3-carbalkoxy-Z-buten-l-yl-triaryl-phosphorane,5-carbalkoxy-3- methyl-2,4-pentadien-1-yl-triaryl-phosphorane and7-carbalkoxy-3-methyl-2,4,6-octatnien l-yl-triaryl-phosphorane anddecomposing the adduct formed as a product of the condensation to obtainan ester represented by the formula CH3 CH3 alkyl wherein R beginningwith methyl, represents alternatehydrogen and m represents an integerfrom 1 to 3, heat- Y a mfimbfil' of the group qonsisting of methyl anding said ester to isomerize the cis-configuration to transg i and m iP gan mteger i 1 2 1 15 configuration and sapom'fying the said ester.

process W m compnses con ensmg 5. A es which co 'ses condensin7-carbethtetramethyl 2,4,6,8,10,12,14 hexadecaheptaen-1,16-daal S i g Ioxy3-methyl-2,4,6-octatr1en l-yl-tr1phenyl-phosphon1um with a member ofthe group consisting of S-carbalkoxyb 2 6 11 1st t th 1 2 4 6 8 10 14 hZ-buten-l-yl-triaryl-phosphorane, 5-carbalkoxy-3-methyl- Tomi e e rama.1 exa- 24 pemadien LYHriarYLPhosPhorane and 7 cal.balkoxydecaheptaen-l,16-d1al and heating the reaction product3-methyl-2,4,6-octatrien-l-yl-triaryl-phosphorane and deto Produce qcomposing the adduct formed as a product of the conden- 10 J 1 1 3 2 3 5dotflacofltapemadecafiflsation to obtain an ester represented by theformula 1,32-dioic acid diethyl ester.

I alkyl alkyl wherein R beginning with methyl, represents alternate- 6.A compound represented by the formula 1y a member of the groupconsisting of methyl and wherein R, beginning with methyl, representsalternately hydrogen and m represents an integer from 1 to 3. a memberof the group consisting of methyl and hydro- 3. A process whichcomprises condensing 2,6,l1,l5- W gen, R represents a member of thegroup consisting of tetramethyl 2,4,6,l0,l2,14-hexadecahexaen-8-yn-l,16- hydrogen and alkyl, and n represents aninteger from dial with a member of the group consisting of 3-carbalkl to3.

oxy-2-buten 1 yl-triaryl-phosphorane, S-carbalkoxy-S- 7. A compoundrepresented by the formula methyLZA-pentadien-l-yl-triaryl-phosphoraneand 7-carbwherein R, beginning with methyl, represents alternatelyalkoxy-3-methyl-2,4,6-octatrien l-yl-triaryl-phosphorane, a member ofthe group consisting of methyl and hydrodecomposing the adduct formed asa product of the 35 gen, R represents a member of the group consistingof condensation to obtain an ester represented by the forhydrogen andalkyl, and n represents an integer from mula 1 to 3.

nlky] alkyl wherein R beginning with methyl, represents alternate- 8.2,6,10,14,19,23,27,31 octamethyl 2,4,6,8,l0,12,l4, ly a member of thegroup consisting of methyl and dotriacontapentadecean 3 hydrogen and mrepresents an integer from 1 to 3 and dioic acid dialkyl estersaponifying the ester thereby obtained. 9. 2,6,10,14,19,23,27,31octamethyl 2,4,6,8,10,l2,14,

A 4 A process which compnses condensing 26,1115 16,l8,20,22,2.,26,28,30dotriacontapentadecaen 1,32

tetramethyl 2,4,6,8,10,l2,14 hexadecaheptaen-l,l6-dial 53 $5 3325 3 7 1116 2O 24 heXamethYL with a member the gwuP wnsisling 3'carbalkmy' 0 l 3579 11 13 15 1719 21 ZZZiS-hexhcdsatridecaene.2-buten-1-yl-triaryl-phosphorane, 5-carbalkoxy-3-methyli ij z g,3,711,1620,24 hexameth 2,4-pentadien-l-yl-triaryl-phosphorane and7-carbalkoxy- 1 5 9 1 113,15,1719,21,23,ZSheXacosatridecaena y Afi- -y y-p p decom- 12. 1,26-dicarbalkoxy 3,7,11,16,20,24 hexamethylposing theadduct formed as the product of the conden-1,3,5,7,9,1l,l5,17,l9,2l,23,25 hexacosadodecaen-13-yne. sation to obtainan ester represented by the formula 5 l3. 1,26-dicarbomethoxy3,7,1l,l6,20,24 hexamethy1-1,3,5,7,9,11,15,17,19,21,23,25hexacosadodecaen 13- yne.

wherein R beginning with methyl, represents alternately a member of thegroup consisting of methyl and No references cited.

6. A COMPOUND REPRESENTED BY THE FORMULA